Name 2 ways that cells in one part of the body can communicate with cells in another part of the body.
1. Via the bloodstream with hormone secretion (endocrine system)
2. The nervous system using neurons.
How does the Endocrine system use chemical to send messages between cell A and cell B?
Endocrine glands secrete hormones into the blood stream and these hormones are accepted by receptor proteins in the cell membrane of target cells.
How does the nervous system use chemicals to send messages between cell A and cell B?
The Nervous system transmits messages via secretion of chemicals from one neuron to another through the synapse. Neurotransmitters leave the first neuron by exocytosis and are recognized by target cell membrane proteins.
What are the 2 parts of the components of the nervous system?
PNS (peripheral nervous system) - spinal nerves and cranial nerves
CNS (central nervous system) - brain and spinal cord.
Neuron pathway for a reflex action (an action that happens automatically without us thinking about it). For example, when the doctor taps your Knee the leg will move automatically. Most sensory neurons in a reflex arc do not go to the brain.
Pathway of the reflex arc?
1. receptor receives a stimulus 2. nerve impulse travels along sensory neuron towards CNS 3. nervous impulse goes to interneuron in spinal chord of goes directly to a motor neuron 4. impulse travel along motor neuron away from CNS towards effector. 5. Effector responds to the initial stimulus.
Label the following diagram of a neuron.
Label with the following labels:
Cell body, nucleus, dendrites, axon, myelin sheath, Schwann cell, nodes of Ranvier, direction of nerve pathway.
A neuron fibre that conducts a signal away from the cell body and toward the next cell or effector.
Description of sensory neuron.
- Long dendrite, short axon.
- Myelinated dendrite and axon.
- Cell body is just outside CNS.
- Cell body is like a bulb.
Description of motor neuron.
- Short dendrite, long axon.
- Myelinated axon.
- Cell body is just inside the CNS.
- Cell body has short dendrites attached to it.
The difference in electrical charge across axon membrane when the neuron is at rest (-65mV)
What do we mean when we say that the membrane of a neuron is polarized?
The axoplasm is more negatively charged than the outer membrane.
How is resting potential generated?
- The inside of the membrane is relatively negative to the outside resulting in a potential difference of -65 mV.
- There are large negatively charged proteins in the axoplasm. The Na+/K+ (sodium potassium) pump used active transport to pump 3 Na+ out and 2K+ in. This makes the outside positive and it sets up the ion gradient (Na+ is high outside and K+ is high inside). The sodium and potassium gates are closed but slightly leaky. The potassium ions leak out faster than the sodium ions leak in, which also helps to establish a build-up of positive charge on the outside and negative on the inside.
What is a nerve impulse?
Once the action potential happens at any one spot on the neuron, it spreads like a wave down the whole neuron. This is the nerve impulse.
Change in voltage on memebrane during the action potential.
- Resting potential - -65mv
- Depolarization inside of membrane becomes more positive.
- Repolarization inside of membrane becomes more negative again.
-Refractory period inside of membrane goes below - 65 mV.
Describe the parts of the action potential.
1. During resting potential the Na+ and K+ channels are closed and resting potential is maintained by the Na+/K+ pump
2. A stimulus opens some Na+ channels; if threshold is reached an action potential is triggered.
3. Depolarization - Additional Na+ channels open, K+ channels are closed; the interior of the cell becomes more positive.
4. Repolarization - Na+ channels close. K+ channels open and K+ rushes out; interior of cell is more negative than outside.
5. The K+ channels close relatively slowly, causing a brief undershoot below resting potential.
6. The Na+/K+ pump reestablishes the resting potential.
An action potential will only occur in a neuron if a certain amount of depolarization occurs.This is called the threshold depolarization. Once
this threshold is reached, the action potential begins.
Short time period during which the membrane becomes hyperpolarized and the voltage goes below the resting potential.
What prevents that action potential from traveling backwards?
Where K+ ions are leaving the axoplasm Na+ channels are still inactivated and therefore an
action potential cannot be generated in this region because sodium ions are on the wrong
side of the membrane.
What is saltatory conduction?
When the action potential jumps from one node to the next as it propagates down the axon or
What happens as the action potential spreads down the neuron?
The action potential spreads through the membrane one step at a time. As one portion of the membrane is depolarizing the area just behind is repolarizing, and the area behind that is going back to its resting state.
Function of the myelin sheath?
1. To insulate against other neurons in the same nerve.
2. Allows for nerve regeneration if a nerve is severed by holding the rest of the nerve together.
3. Increases the rate of conduction of a nerve impulse by allowing for saltatory conduction. Impulse can be up to 1000 times faster.
Know the various parts of the synapse.
Axon bulb, presynaptic membrane, postsynaptic membrane, synaptic vesicles, neurotransmitters, receptor sites on receptor protein.
Explain the process by which impulses travel across a synapse.
1. The action potential reaches the axon bulb.
2. Ca2+ ions move into the axon bulb through channels and cause synaptic vesicles to fuse with the presynaptic membrane and release their neurotransmitter into the synaptic cleft (by exocytosis). Filaments in the axon bulb help to pull the vesicles over to the edge of the cell.
3. The neurotransmitter diffuses across the synaptic cleft and binds to receptor proteins on postsynaptic membrane (fit like "lock and key"). The receptor proteins open and ions move in or out of the cell, depending on whether it is an excitatory or inhibitory synapse.
4. The postsynaptic membrane is either depolarized (excitatory synapse) or hyperpolarized (inhibitory synapse). Excitatory synapses open sodium ion channels, and inhibitory synapses open potassium ion channels.
5. If enough excitatory synapses occur in the second neuron and the threshold is reached in the postsynaptic cell, the action potential will be initiated in the second neuron, and travel down its axon.
Describe how neurotransmitters are broken down in the synaptic cleft.
An enzyme (eg acetylcholinerase) is released into the synaptic cleft breaks down the neurotransmitter (eg acetylcholine) to prevent continuous stimulation of the postsynaptic
Why can the synapse only go in one direction?
Note that the synapse can only go in one direction, because the presynaptic cell contains the neurotransmitter and the postsynaptic cell has the receptors.
What is the difference between and excitatory and an inhibitory synapse?
Excititory synapses cause Na+ to enter cell and depolarize the post synaptic membrane. This leads to and action potential if the threshold is reached.
An inhibitory synapse causes K+ to leave the cell and hyperpolarize the membrane. This inhibits the action potential.
WHat determines whether or not the post synaptic cell with develop an action potential?
A synapse which hyperpolarises the membrane will lead to inhibition of the neuron, because it pushes the membrane potential below the threshold value. Conversely, a synapse which depolarises the membrane will lead to excitation of the neuron, because it pushes the membrane potential above the threshold value. An excitatory synapse opens sodium gates, whereas an inhibitory synapse opens K+ gates.
What are some of the major neurotransmitters?
Acetylcholine - excitatory in skeletal muscles but inhibitory in other areas.
Norepinephrine (related to adrenalin) - excitatory or inhibitory (gets you ready for emergencies.\
Dopamine - generally excitatory but may be inhibitory at some sites
Serotonine - generally inhibitory.
How do drugs effect the synapse?
The effect they have depends on whether it is an excitatory or inhibitory synapse and on the drug itself.
What are the five components of a reflex arc?
Sensory receptor - affector
Sensory neuron - afferent neuron
Motor neuron - efferent neuron
Muscle or gland - Effector
Is it necessary for the brain to be involved in a reflex arc? Explain.
The brain is not involved initially, but at the same time as an impulse is transmitted along the motor neuron, another impulse is transmitted along an interneuron to notify the brain. The brain will be involved in making an integrated decision.
What are the functions of the central nervous system?
Receive sensory input from the sensory neurons.
- Integrate all the information coming from the sensory neurons and decide on an
appropriate motor response.
- Send appropriate response to the motor neurons.
What are the functions of the peripheral nervous system?
Receive environmental stimuli from receptor cells and conduct sensory
information towards the central nervous system.
- Carry nerve impulses from the central nervous system to the effectors (muscles
Dorsal root ganglion?
A lump of cell bodies of the sensory neurons on the outside of the spine in the dorsal route.
What are the meninges?
Continuous membranes surrounding the brain and spinal chord. Cerebrospinal fluid flows between them.
Controls autonomic, homeostatic functions including: breathing, heart and blood vessel activity, swallowing, digestion and vomiting.
Cerebrum (cerebral cortex)?
Integrating center for memory, learning, emotions, and other highly complex functions of the central nervous system; initiation of somatic motor responses (skeletal muscle contractions).
the "main input center for sensory information going to the cerebrum and the main output center for motor information leaving the cerebrum. Incoming information from all the senses is sorted in the thalamus and sent to the appropriate cerebral centers for further processing. The thalamus also receives input from the cerebrum and other parts of the brain that regulate emotion and arousal."
Maintenance of homeostasis, particularly in coordinating of endocrine and nervous systems (neuroendocrine control center - N5); secretes hormones of the posterior pituitary and releasing factors, which regulate the anterior pituitary - N5;
involved in osmoregulation, contractions of uterus, control of sexual cycles, milk production, control of thyroid gland, etc.
A thick band of nerve fibres that connect the right and left cerebral hemispheres and enable the hemispheres to process information together.
Expalin how the hypothalamus and pituitary gland interact as the neuroendocrine control centre.
The pituitary gland (an endocrine gland) is attached to the hypothalamus of the brain
(nervous system), hence, the term neuroendocrine.
- The pituitary gland send various hormones out into the blood when it receives messages from the hypothalamus.
How do the hypothalamus and the posterior pituitary work together?
Neurosecretory cells in the hypthalamus have axons that end in the posterior pituitary and secrete their hormone into the blood in the posterior pituitary. 1. ADH controls blood osmolarity and blood pressure 2. Oxytocin stimulates uterus to contract when baby is being born and milk let down in mammary glands.
How do hypothalamus and anterior pituitary work together?
-The anterior pituitary gland is stimulated by releasing hormones from the hypothalamus.
- Some of the hormones released by the anterior pituitary are:
o-FSH to stimulate follicle development in females and sperm production in males.
- LH to stimulate the corpus luteum in females and testosterone production in
- Growth hormone to stimulate growth of bones.
- Prolactin to stimulate milk production
Autonomic nervous system?
Part of the motor division of the peripheral nervous system it stimulates involuntary muscles in the body - cardiac and smooth muscles.
Somatic nervous system?
Part of the motor division of the peripheral nervous system. It stimulates the voluntary skeletal muscles.
Sympathetic division of autonomic nervous system?
Involved in speeding up your system for "fight or flight". Eg. it speeds up heart rate, dilated pupils.
Parasympathetic division of autonomic nervous system?
Involved in bringing body functions back to normal (relaxed response) after fight or flight reaction. Eg. heart rate slows down, pupils constrict etc.
Which neurotransmitter is used by the sympathetic division?
Norepinephrine (adrenalin) and epinephrine
What is the source gland for adrenaline (epinephrine)
The adrenal medulla which is found in the center part of the adrenal gland. Adrenal gland is above the kidney.
In what way is the endocrine gland actually 2 glands in one?
The adrenal gland has an outer part called the adrenal cortex and an inner part called the adrenal medulla. The adrenal cortex produces aldosterone, and the adrenal medulla produces epinephrine and norepinephrine.
What is the role of adrenalin in the "fight or flight" response?
Dilates pupils, increases heart rate, increases concentration of glucose in blood) because glycogen in converted to glucose), increases blood flow to skeletal muscles, increases blood pressure, increases heart rate.